1. Technical Field
The present invention relates to electric power conversion apparatuses that include means for cooling semiconductor modules that form electric power conversion circuits.
2. Description of the Related Art
Electric power conversion circuits, such as a DC-DC converter circuit and a DC-AC inverter circuit, are used in generating, for example, drive power for driving AC motors that make up power sources of motor vehicles, such as an electric vehicle and a hybrid vehicle.
Moreover, for enabling an AC motor to generate high torque, it is generally necessary to drive the AC motor with large drive power. Accordingly, in an electric power conversion circuit for generating the drive power for driving the AC motor, semiconductor modules generally generate a large amount of heat; the semiconductor modules include therein power semiconductor elements, such as an IGBT (Insulated Gate Bipolar Transistor), for forming the electric power conversion circuit. Therefore, it is also necessary to cool the semiconductor modules.
To solve the above problem, Japanese Patent Application Publications No. 2007-166819 and No. 2007-166820 disclose a technique according to which cooling pipes are alternately stacked with the semiconductor modules. Consequently, a coolant can flow through the cooling pipes, thereby cooling the semiconductor modules.
More specifically, as shown in FIG. 11, the semiconductor modules 921 are alternately stacked with the cooling pipes 922 in a stacking direction (i.e., the direction perpendicular to the paper surface of FIG. 11) to form a stacked body 92. Further, the stacked body 92 is received in a frame 93. The frame 93 has an opening 931 that opens in a direction perpendicular to the stacking direction (i.e., the upward direction in FIG. 11).
Furthermore, in the frame 93, a pressing member (not shown), which presses the stacked body 92 in the stacking direction, is disposed at one end of the stacked body 92 in the stacking direction. Moreover, each of the semiconductor modules 921 includes a plurality of control terminals 923 that are connected to a control circuit board 94. The control circuit board 94 makes up part of the electric power conversion circuit.
The frame 93 also has a bottom wall 932 and a plurality of side walls 933. The bottom wall 932 is formed on the opposite side to the opening 931 of the frame 93 in the direction perpendicular to the stacking direction (i.e., the vertical direction in FIG. 11). The side walls 933 each extend perpendicular to the bottom wall 932 and together define the opening 931 of the frame 93. That is, the internal space of the frame 93 is completely opened, by the opening 931, on the opposite side to the bottom wall 932. Moreover, each of the side walls 933 has, at its end on the opening 931 side (i.e., at its upper end in FIG. 11), a fixing portion 935 for fixing the control circuit board 94.
With the above configuration, however, the rigidity of the frame 93 may be low on the opening 931 side because the frame 93 is completely opened by the opening 931. Consequently, with the low rigidity, the side walls 933 of the frame 93 may be easily caused, for example by external vibration transmitted to the electric power conversion apparatus 9, to vibrate on the opening 931 side (i.e., on the upper side in FIG. 11). Further, the vibration of the side walls 933 may induce stress in the control circuit board 94 that is fixed to the fixing portions 935 of the side walls 933. As a result, due to the stress induced in the control circuit board 94, connection failure may occur between the control circuit board 94 and the control terminals 923 of the semiconductor modules 921.